Small – But Not Easy: Evaluation of Sampling Methods in Floodplain Lakes Including Whole-lake Sampling
We tested the efficiency of electrofishing and beach seining with several sampling strategies in small (<1 ha) floodplain borrow pits of the Dyje River (Danube basin). The study sites were characterized as rectangular-shaped with maximum depths of 2m, having uniform habitat with minimal shelters and gravel bottom with organic sediment. We conducted point abundance sampling and continual electrofishing along the shoreline and also sampled in a zigzag pattern in the mid-zone from a boat. Sub-sampling and whole-lake sampling was conducted using a beach seine (40m length, 10mm mesh size). Each of the four sampling strategies (point sample electrofishing, continuous electrofishing, seining sub-samples, and whole-lake seining) was conducted on separate days in two sampling events in November 2005 and May 2007. A total of 22 species was registered in both sites. Electrofishing was more efficient for determining species richness in both sites compared to seining in the November sampling, but this finding was reversed in May 2007. Some species (chub, weatherfish) were recorded only by electrofishing, while other species (perch, bitterling, tench) were recorded mainly by electrofishing. Asp and blue bream were recorded only by seining. Pelagic species (bleak, bream, white bream) were highly underestimated by electrofishing in both sites and sample periods. The accurate representation of the fish community using just one sampling method and strategy is not feasible even in a small floodplain lake. Whole-lake seining through the entire borrow-pit site was more representative for pelagic species but less efficient for shelter-seeking species. Regarding the ability to capture representative samples, the behaviour of particular fish species seems to be a more significant factor than fish size.
Jurajdaa, P., M. Janáč, S.M. White, and M. Ondračková. 2009. Small – but not easy: Evaluation of sampling methods in floodplain lakes including whole-lake sampling. Fisheries Research 96(1):102–108. Online at https://www.sciencedirect.com/science/article/abs/pii/S0165783608002877.